But whenever one discusses the idea that buying local food saves fuel, the naysayers show up. After all, there is the study from New Zealand's Lincoln University that proved New Zealand lamb transported to the UK to have a carbon footprint of only 688 kg per tonne shipped, vs the purported 2,849 kg footprint of UK raised lamb. (They evidently use a lot less fertilizer and feed in New Zealand). Strawberry Fields Forever.

Then there are the California strawberries, where (like Captain Queeg in The Caine Mutiny, talking of another batch of strawberries), Naysayer-in Chief Professor Pierre Desrochers "proved beyond the shadow of a doubt and with... geometric logic" that growing them in California instead of locally allows "for a much more intensive and efficient use of fuel, capital, machinery and other resources."

And of course there are all those SUVs driving to meet the farmers in pickup trucks, what about the carbon footprint of that, compared to the efficiency of a big truck? (As if they would not be driving the SUV to the grocery as well.)

1. The Shipping Problem

There is no question, shipping frozen lamb by sea from New Zealand to the UK has been pretty efficient. One can say the same thing for Australian wine in glass bottles -- the last couple of miles by truck burn almost as much as the entire sea voyage.

Shipping that lamb is cheap only because it doesn't include the externalities, such as the cost in soot and pollution from burning the crap from the bottom of the barrel. Factor that in, and the local UK lamb begins to look a lot better.

Peak Guano: Harvesting the last of the natural fertilizer off Peru. Tomas Munita for The New York Times

2. The Fertilizer Problem

Economist Paul Kedrosky noted that a ton of fertilizer is made with 33,500 cubic feet of natural gas. Right now, the stuff is cheap, thanks to new unconventional sources like shale gas, though these have their own environmental issues (see Jargon Watch: Fracking)

Then there is peak phosphorus. Without the stuff, we simply cannot grow food. Our food system works because of artificial fertilizer made from natural gas and phosphorus dug out of Saskatchewan or guano carved off islands in the Pacific. But we're getting close to running out of the stuff. A hundred and fifty years ago, there was a very simple and logical way of dealing with this problem: People came around and took away human waste and urine and put it back on the farms surrounding the communities. Indoor plumbing (and a lot of available horse manure) put an end to this. But Instead of us pissing away phosphates and flushing away perfectly good manure from well-fed people, we could put it to use in a localized food system that wouldn't need artificial fertilizers and mined phosphates.

A relocalized food system, combined with a redesigned plumbing system that separates and captures urine for phosphorus such as they have in parts of Sweden, could reduce the need for using natural gas for fertilizer or fuel to move it and phosphates around the country.

3. The Seasonal Problem

Another argument often raised in opposition to a localized diet is the cost of heating greenhouses to get local produce out of season. The Telegraph wrote:

The energy used to produce out-of-season lettuces in winter in Britain was greater than importing lettuces from Spain. [Dr Llorenç Milà I Canals, of Surrey University] added: "If you are producing lettuce in a heated glasshouse in the UK, the amount of energy you are using is huge, so in that case buying British produce over winter is a bad idea."

This may well be true. But the fact of the matter is, you can't separate a local diet from a seasonal diet. You shouldn't be buying hothouse lettuce and tomatoes, you should be eating them when they are in season.

My wife Kelly writes about food for Planet Green and TreeHugger, and for the last two winters, we have essentially eaten a 19th century diet where we gorge on fresh vegetables in season all summer, and eat a lot of root vegetables all winter. It is, admittedly, an extreme position, taken for the purpose of her writing, and it takes a lot of time that most people do not have, both in the winter cooking, and right now while she is canning. Her attitude is that "if it is available here, then I will eat it in season," limiting her purchases of imported food to items like lemons that we never get here.

But my 91-year-old mother, who thinks air freighted asparagus from Peru is the greatest thing that ever happened, is appalled that anyone would want to live this way.

My mom, like all of us, has enjoyed it because cheap energy has made refrigeration and transport cheap; nobody has to think about seasons anymore. But if you follow the seasons, get into the flavours and the differences, enjoy the thrill of the first local strawberry of spring, it actually tastes better, is certainly healthier and is often cheaper.

San Francisco Farmers Market in 1951, before centralized delivery. Should we go back?

In the worst scenario, a UK consumer driving six miles to buy Kenyan green beans emits more carbon per bean than flying them from Kenya to the United Kingdom.

It is probably all true, because the system is in transition and there is just the beginning of an infrastructure capable of supporting local food. Even Prince Charles got caught up in it. But as we transition away from shipping food around the globe and into producing and eating more local, in-season foods, that infrastructure will have to expand and evolve to serve a larger population.

Hub and Spoke system: Our food is currently distributed by semitrailer from huge food terminals and warehouses, for the convenience of the big stores selling high volumes.

The current system is set up to deal with a system that moved stuff around the world in great quantities, with great efficiency. It was a hub-and-spoke system, which dealt with the quantities and got them where they needed to go, through massive food terminals and warehouses. Entire ecosystems have become monocultures to continue to supply them, at the expense of the local markets, which, often being small, became too expensive and complicated to serve.

Peer to Peer system, where customers can interact directly with suppliers.

But we now have the technology now to turn this system on its head. Peer-to-peer systems (Prince Charles would feel at home) can connect the farmer with his market. In Ontario, Canada, Lori Stahlbrand established Local Food Plus, a service that connects farmers to consumers on a peer-to-peer basis. She claims that if 10,000 people convert to local, sustainable food, it would reduce greenhouse gas emissions by the equivalent of taking a thousand cars off the road, and would create 100 new jobs.

Ultimately, to call out the current inefficiencies of the farmers' market as a way to justify our industrialized, globalized food system is like scrapping a car at the junkyard because it needs an oil change.

It isn't just about growing our food locally and buying it at the farmers market. To really change our food system so that we are not eating fossil fuels we have to look at the way our cities are designed, how our waste system works, how the distribution system is set up, and what we do in the developing world that has become our out-of-season supplier.